Add a configuration for b2120stxh407 ST boards

Change-Id: I0f4adb7cb4057583c2af6e7be1aaaea79c821a7f
Use /system/bin/sh instead of mksh

sh exists on all Android platforms, mksh
no longer does. Closes: #199

Change-Id: I61ba1a01bb9540443db971cb23dac7e744eae44b
LAVA-1462 - add elapsed time support

Change-Id: Ia2fe7f970b5e33ea20a465e06ae9c90838e1d605
Drop use of 'tr' as some Android images omit 'tr'

lava-send needs the MultiNode API library to use awk
instead of relying on support for 'tr'. Closes: #214
Ensure key=value pairs with empty values are dropped.
Allow for internal calls to use different behaviour.

Change-Id: I3542fb1980ed01bdad8e7199d42f8a4b52dc8c83
tr needs to be provided as well as awk - both are busybox applets.

This reverts commit df79dabf30095f4ee7686defe17efd5ad1de1288.

Change-Id: I2d004300ed1e9f4c17e14ea7f884cfbd7459de95